Heat treatment method and heat treatment apparatus

ABSTRACT

The number of substrates held by a substrate holder is increased compared with conventional techniques while uniformity of a heat treatment is ensured. The substrate holder holds a plurality of substrates at predetermined vertical intervals. The substrate holder is carried into a heat treating furnace. A predetermined heat treatment is performed on the substrates. The substrate holder has two holder constituting bodies. Each of the holder constituting bodies has a plurality of columns and substrate holding sections. The columns are arranged on the circumference of the same imaginary circle. The substrate holding sections hold circumferential portions of the respective substrates. One of the holder constituting bodies holds the substrates under the condition that front surfaces of the substrates face upward, while the other of the holder constituting bodies holds the substrates under the condition that back surfaces of the substrates face upward. The substrate with the front surface facing upward and the substrate with the back surface facing upward are alternately arranged in a vertical direction. At least one of the holder constituting bodies moves in the vertical direction to change the positions of the holder constituting bodies relative to each other. A distance between one of a first pair of substrates that are vertically adjacent to each other and have the respective front surfaces facing each other and the other of the first pair of substrates is set to ensure uniformity of the treatment and larger than a distance between one of a second pair of substrates that are vertically adjacent to each other and have the respective back surfaces facing each other and the other of the second pair of substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application benefits from Japanese applicationsJP2007-249039 and JP2007-249040 filed on Sep. 26, 2007, the disclosureof which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat treatment method and a heattreatment apparatus, and more particularly to a technique for performinga heat treatment on an increased number of substrates with uniformity ofthe treatment ensured.

2. Description of the Related Art

In the process for manufacturing semiconductor devices, varioustreatment apparatuses (semiconductor manufacturing apparatuses) are usedto perform treatments such as oxidization, diffusion, and chemical vapordeposition (CVD) on substrates to be treated, e.g., semiconductor wafers(hereinafter also referred to as wafers). As one of the treatmentapparatuses, a heat treatment apparatus is known, which is capable ofperforming a heat treatment on multiple substrates simultaneously.

The abovementioned heat treatment apparatus has a heat treating furnaceand a boat. The boat is a substrate holder, which holds multiple wafersat a predetermined vertical interval and is carried into and out of theheat treating furnace (refer to JP-A-2001-223254). In addition, the heattreatment apparatus includes an elevation mechanism and a transfermechanism. The elevation mechanism and the transfer mechanism arelocated in a loading area (operation area) present under the heattreating furnace. The elevation mechanism is operable to lift and lowera lid under the condition that the boat is placed on a thermalinsulation tube (that is furnace throat heat insulating means) presenton the lid for closing the furnace throat in order that the boat iscarried into the heat treating furnace from the loading area and carriedout of the heat treating furnace into the loading area. The transfermechanism is operable to transfer wafers between the boat carried intothe loading area and a container capable of accommodating the wafers.

The boat has a plurality of columns between a bottom plate and a topplate. Each of the columns has substrate holding sections arranged at apredetermined vertical interval (pitch). The substrate holding sectionsare grooves or protrusions for holding edge portions of the wafers. Allthe wafers are held by the boat under the condition that front surfaces(to be treated) of the wafers face upward.

However, the minimum pitch of the substrate holding sections, whichdepends on the number of wafers to be held by the boat, is determinedbased on uniformity of the surface (to be treated) of each of thewafers, uniformity between the surfaces (to be treated) of the wafersand the number of the wafers to be placed. It is, therefore, difficultto increase the number of wafers to be held by the boat. If the pitch isincreased to improve the uniformity of the surface of each of the wafersand the uniformity between the surfaces of the wafers, the number of thewafers is reduced.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a heattreatment method and a heat treatment apparatus, which are capable ofsolving the problems of the conventional technique and increasing thenumber of wafers held by a substrate holder compared with theconventional techniques while uniformity of the treatment is ensured.

According to a first aspect of the present invention, a heat treatmentmethod, in which a plurality of substrates to be treated is held by asubstrate holder at predetermined vertical intervals, the substrateholder is carried into a heat treating furnace, and a predetermined heattreatment is performed on the substrates, comprises the steps of:arranging the substrates in the substrate holder such that frontsurfaces or back surfaces of the substrates vertically adjacent to eachother face each other; and setting a first distance between one of afirst pair of substrates that are vertically adjacent each other andhave the respective front surfaces facing each other and the other ofthe first pair of substrates to ensure uniformity of the treatment, andsetting a second distance between one of a second pair of substratesthat are vertically adjacent each other and have the respective backsurfaces facing each other and the other of the second pair ofsubstrates to be smaller than the first distance.

According to a second aspect of the present invention, in the heattreatment method, the substrate holder is composed of two holderconstituting bodies; each of the holder constituting bodies has aplurality of columns each including a plurality of substrate holdingsections, the substrate holding sections of each of the holderconstituting bodies being arranged at a predetermined vertical intervaland adapted to hold circumferential portions of the substrates, thecolumns being arranged on the circumference of the same imaginarycircle; one of the holder constituting bodies holds the substrates underthe condition that the front surfaces of the substrates face upward, andthe other of the holder constituting bodies holds the substrates underthe condition that the back surfaces of the substrates face upward, sothat the substrate with the front surface facing upward and thesubstrate with the back surface facing upward are alternately arrangedin a vertical direction; and at least one of the two holder constitutingbodies moves up and down to change the positions of the two holderconstituting bodies relative to each other so that the first distance isset to ensure the uniformity of the treatment and larger than the seconddistance.

According to a third aspect of the present invention, the heat treatmentmethod further comprises the step of pivoting at least one of the twoholder constituting bodies in the circumferential direction to changethe positions of the two holder constituting bodies relative to eachother so that the columns surround the circumferential portions of thesubstrates under the condition that the distance between any two of thecolumns is smaller than the diameters of the substrates.

According to a fourth aspect of the present invention, a heat treatmentapparatus comprises a substrate holder for holding a plurality ofsubstrates at predetermined vertical intervals and a heat treatingfurnace for receiving the substrate holder and allowing a predeterminedheat treatment to be performed on the substrates therein, wherein thesubstrate holder has a plurality of substrate holding sections forholding end portions of the substrates under the condition that thesubstrate having a front surface facing upward and the substrate havinga back surface facing upward are alternately arranged in a verticaldirection; and the substrate holding sections are arranged such that afirst distance between one of a first pair of substrates that arevertically adjacent each other and have the respective front surfacesfacing each other and the other of the first pair of substrates is setto ensure uniformity of the treatment and larger than a second distancebetween one of a second pair of substrates that are vertically adjacenteach other and have the respective back surfaces facing each other andthe other of the second pair of substrates.

According to a fifth aspect of the present invention, in the heattreatment apparatus, the substrate holder is composed of two holderconstituting bodies; each of the holder constituting bodies has aplurality of columns each including a plurality of substrate holdingsections, the substrate holding sections of each of the holderconstituting bodies being arranged at a predetermined vertical intervaland adapted to hold circumferential portions of the substrates, thecolumns being arranged on the circumference of the same imaginarycircle; one of the holder constituting bodies holds the substrates underthe condition that the front surfaces of the substrates face upward; theother of the holder constituting bodies holds the substrates under thecondition that the back surfaces of the substrates face upward; the twoholder constituting bodies are combined such that the substrate with thefront surface facing upward and the substrate with the back surfacefacing upward are alternately arranged in the vertical direction; and atleast one of the two holder constituting bodies is capable of moving upand down by a vertical movement mechanism to change the positions of thetwo holder constituting bodies relative to each other in order that thefirst distance is set to ensure the uniformity of the treatment andlarger than the second distance.

According to a sixth aspect of the present invention, in the heattreatment apparatus, a substrate holder rotating mechanism is providedunder a lid for closing a furnace throat of the heat treating furnaceand has a rotating shaft; and the vertical movement mechanism has anelevation shaft and an elevation drive section, the elevation shaftextending through the rotating shaft of the substrate holder rotatingmechanism and being capable of moving up and down, the elevation drivesection being adapted to cause the elevation shaft to move up and down.

According to a seventh aspect of the present invention, in the heattreatment apparatus, a thermal insulation tube is provided on the lidfor closing a furnace throat of the heat treating furnace; the verticalmovement mechanism is composed of an elevation mechanism and a latchmechanism; the elevation mechanism carries holder constituting bodies ofthe substrate holder into and out of the heat treating furnace; and thelatch mechanism latches one of the holder constituting bodies when thesubstrate holder is carried out of the heat treating furnace to restorethe relationship between the position of the one of the holderconstituting bodies relative to the position of the other of the holderconstituting bodies.

According to an eighth aspect of the present invention, the heattreatment apparatus further comprises a pivoting mechanism for pivotingat least one of the holder constituting bodies in the circumferentialdirection to change the positions of the two holder constituting bodiesrelative to each other in order that the columns of the holderconstituting bodies surround the circumferential portions of thesubstrates under the condition that a distance between any two of thecolumns is smaller than the diameters of the substrates.

According to a ninth aspect of the present invention, in the heattreatment apparatus, a substrate holder rotating mechanism is providedunder the lid for closing a furnace throat of the heat treating furnaceand has a rotating shaft, and the pivoting mechanism has an elevationshaft extending through the rotating shaft and being capable of pivotingand moving up and down the holder constituting body.

According to a tenth aspect of the present invention, in the heattreatment apparatus, the pivoting mechanism is composed of a latchmechanism and a substrate holder rotating mechanism; the latch mechanismlatches one of the holder constituting bodies when the substrate holderis carried out of the heat treating furnace to restore the relationshipbetween the vertical position of the one of the holder constitutingbodies relative to the vertical position of the other of the holderconstituting bodies; and the substrate holder rotating mechanism pivotsthe other of the holder constituting bodies in the circumferentialdirection by a predetermined angle with respect to the holderconstituting body latched by the latch mechanism.

According to an eleventh aspect of the present invention, a heattreatment method, in which a plurality of substrates to be treated isheld by a substrate holder at predetermined vertical intervals, thesubstrate holder is carried into a heat treating furnace, and apredetermined heat treatment is performed on the substrates, comprisesthe steps of: forming a multi-plate unit that uses a support ring tohold circumferential portions of two substrates under the condition thatback surfaces of the two substrates face each other; and holding aplurality of the multi-plate units by means of the substrate holder at avertical interval larger than a distance between the front surface ofone of the two substrates held by the multi-plate unit and the backsurface of the other of the two substrates such that a first distancebetween one of a first pair of substrates that are vertically adjacenteach other and have the respective front surfaces facing each other andthe back surface of the other of the first pair of substrates is largerthan a second distance between one of a second pair of substrates thatare vertically adjacent each other and have the respective back surfacesfacing each other and the other of the second pair of substrates.

According to a twelfth aspect of the present invention, in the heattreatment method, each of the support rings has a first support ring anda second support ring; each of the first support rings holds thesubstrate under the condition that the back surface of the substratefaces upward; and each of the second support rings holds the substrateunder the condition that the front surface of the substrate facesupward.

According to a thirteenth aspect of the present invention, in the heattreatment method, each of the first and second support rings hasprotrusions that protrude from the circumference thereof and arearranged at an appropriate interval; the protrusions of the secondsupport ring of each of the support rings are placed on the protrusionsof the first support ring of the support ring, and have respectivethicknesses that allow a distance between the substrate held by thefirst support ring and the substrate held by the second support ring tobe maintained to a predetermined value.

According to a fourteenth aspect of the present invention, a heattreatment method, in which a plurality of substrates to be treated isheld by a substrate holder at predetermined vertical intervals, thesubstrate holder is carried into a heat treating furnace, and apredetermined heat treatment is performed on the substrates, comprisesthe steps of: holding the substrates at predetermined vertical intervalsunder the condition that back surfaces of the substrates face upward;forming a single-plate unit that uses a support ring to hold acircumferential portion of one of the substrates under the conditionthat a front surface of the substrate faces upward; and causing thesubstrate holder to hold the single-plate units by means of the supportrings under the condition that the back surface of the substrate held byeach of the single-plate units and the back surface of the substratethat is held by the substrate holder and located directly under thesubstrate held by the single-plate unit face each other such that afirst distance one of a first pair of substrates that are verticallyadjacent each other and have the respective front surfaces facing eachother and the other of the first pair of substrates is larger than asecond distance between one of a second pair of substrates that arevertically adjacent each other and have the respective back surfacesfacing each other and the other of the second pair of substrates.

According to a fifteenth aspect of the present invention, in the heattreatment method, the substrate holder has a plurality of columnssurrounding the end portions of the substrates; and each of the columnshas claws and unit support sections, the claws holding the substrates,the unit support sections holding the single-plate units by means ofprotrusions of the support rings.

According to a sixteenth aspect of the present invention, a heattreatment apparatus holds a plurality of substrates at predeterminedvertical intervals by means of a substrate holder, carries the substrateholder into a heat treating furnace, and performs a predetermined heattreatment on the substrates, wherein the substrate holder has aplurality of columns and a plurality of support rings; the support ringshold circumferential portions of the substrates to constitute aplurality of multi-plate units under the condition that back surfaces oftwo substrates held by each of the multi-plate units face each other;each of the columns has claws arranged in a vertical direction; theclaws hold the support rings that hold the substrates such that adistance between upper surfaces of the claws vertically adjacent to eachother is larger than a distance between the front surface of one of thetwo substrates held by the multi-plate unit and the back surface of theother of the two substrates; and a first distance between one of a firstpair of substrates that are vertically adjacent each other and have therespective front surfaces facing each other and the other of the firstpair of substrates is larger than a second distance between one of asecond pair of substrates that are vertically adjacent each other andhave the respective back surfaces facing each other and the other of thesecond pair of substrates.

According to a seventeenth aspect of the present invention, in the heattreatment apparatus, each of the support rings is composed of a firstsupport ring and a second support ring, each of the first support ringsholding the substrate under the condition that the back surface of thesubstrate faces upward, each of the second support rings holding thesubstrate under the condition that the front surface of the substratefaces upward.

According to an eighteenth aspect of the present invention, in the heattreatment apparatus, each of the first and second support rings hasprotrusions that protrude from the circumference thereof and arearranged at an appropriate interval; and the protrusions of the secondsupport ring of each of the support rings are placed on the protrusionsof the first support ring of the support ring and have respectivethicknesses that allow a distance between the substrate placed on thefirst support ring of the support ring and the substrate placed on thesecond support ring to be maintained to a predetermined value.

According to a nineteenth aspect of the present invention, a heattreatment apparatus holds a plurality of substrates at predeterminedvertical intervals by means of a substrate holder, carries the substrateholder into a heat treating furnace, and performs a predetermined heattreatment on the substrates, wherein the substrate holder has aplurality of columns and a plurality of support rings; each of thesupport rings holds a circumferential portion of one of the substratesto constitute a single-plate unit under the condition that a frontsurface of the substrate held by the single-plate unit faces upward;each of the columns has claws and unit support sections, the claws ofeach of the columns holding the substrates at the predetermined verticalinterval under the condition that the back surfaces of the substratesface upward, the unit support sections holding the single-plate units bymeans of the support rings under the condition that the back surface ofthe substrate held by the claws and the back surface of the substratethat is held by the single-plate unit and located directly above thesubstrate held by the claws face each other; and a first distancebetween one of a first pair of substrates that are vertically adjacenteach other and have the respective front surfaces facing each other andthe other of the first pair of substrates is larger than a seconddistance between one of a second pair of substrates that are verticallyadjacent each other and have the respective back surfaces facing eachother and the other of the second pair of substrates.

According to a twentieth aspect of the present invention, in the heattreatment apparatus, the support ring of each of the single-plate unitshas protrusions that protrude from the circumference thereof and arearranged at an appropriate interval; and the unit support sections holdthe protrusions.

According to the present invention, the substrate holder holds thesubstrates to be treated such that the substrate with the front surfacefacing upward and the substrate with the back surface facing upward arealternately arranged in the vertical direction. The first distancebetween the front surface of one of the first pair of substrates thatare vertically adjacent to each other and have the respective frontsurfaces facing each other and the back surface of the other of thefirst pair of substrates is set to ensure uniformity of the treatmentand larger than the distance between the front surface of one of thesecond pair of substrates that are vertically adjacent to each other andhave the respective back surfaces facing each other and the back surfaceof the other of the second pair of substrates. The number of substratesheld by the substrate holder is therefore increased compared withconventional techniques while the uniformity of the treatment isensured. When the number of the substrates held by the substrate holderis the same as that in the conventional techniques and the distancebetween the front surface of one of the first pair of substrates thatare vertically adjacent to each other and have the respective frontsurfaces facing each other and the back surface of the other of thefirst pair of substrates is increased, the uniformity of the treatmentcan be further improved while the number of the substrates ismaintained.

According to the present invention, the substrate holder is composed ofthe two holder constituting bodies. Each of the holder constitutingbodies has substrate holding sections and the plurality of columns. Thesubstrate holding sections hold the end portions of the substrates. Thecolumns are arranged on the circumference of the same imaginary circle.One of the holder constituting bodies holds the substrates under thecondition that the front surfaces of the substrates face upward, whilethe other of the holder constituting bodies holds the substrates underthe condition that the back surfaces of the substrates face upward. Thesubstrate with the front surface facing upward and the substrate withthe back surface facing upward are alternately arranged in the verticaldirection. At least one of the holder constituting bodies moves up anddown to change the positions of the holder constituting bodies relativeto each other in order that the first distance between the front surfaceof one of the first pair of substrates that are vertically adjacent toeach other and have the respective front surfaces facing each other andthe back surface of the other of the first pair of substrates is set toensure the uniformity of the treatment and larger than the distancebetween the front surface of one of the second pair of substrates thatare vertically adjacent to each other and have the respective backsurfaces facing each other and the back surface of the other of thesecond pair of substrates. The number of the substrates is thereforeincreased compared with the conventional techniques while the uniformityof the treatment is ensured. When the number of the substrates held bythe substrate holder is the same as that in the conventional techniques,and the first distance between the front surface of one of the firstpair of substrates that are vertically adjacent to each other and havethe respective front surfaces facing each other and the back surface ofthe other of the first pair of substrates is increased, the uniformityof the treatment can be further improved while the number of thesubstrates is maintained.

According to the present invention, at least one of the two holderconstituting bodies pivots in the circumferential direction to changethe positions of the two holder constituting bodies relative to eachother in order that the columns surround the end portions of thesubstrates under the condition that the distance between any two of thecolumns is smaller than the diameters of the substrates. This preventsthe substrates from sliding and falling out of the substrate holder.

According to the present invention, the vertical movement mechanism andthe pivoting mechanism can be easily configured.

According to the present invention, each of the multi-plate units usesthe support ring to hold the end portions of the two substrates underthe condition that the back surfaces of the two substrates face eachother. The substrate holder holds the plurality of multi-plate units ata vertical interval larger than the distance between the front surfaceof one of the two substrates held by the multi-plate unit and the backsurface of the other of the two substrates. Therefore, the distancebetween the front surface of one of the two substrates held by themulti-plate unit and the back surface of the other of the two substratesis smaller than the distance between the front surface of the lower oneof the two substrates held by the multi-plate unit and the back surfaceof the substrate located directly under the lower one of the twosubstrates. The number of the substrates held by the substrate holdercan be increased while the uniformity of the treatment is ensured.

According to the present invention, each of the support rings iscomposed of the first and second support rings. Each of the firstsupport rings holds the substrate under the condition the back surfaceof the substrate faces upward. Each of the second support rings holdsthe substrate under the condition the front surface of the substratefaces upward. Each of the support rings therefore holds the twosubstrates under the condition that the back surfaces of the twosubstrates face each other.

According to the present invention, each of the first and second supportrings has protrusions that protrude from the circumference thereof andare arranged at an appropriate interval. The protrusions of the secondsupport ring of each of the support rings are placed on the protrusionsof the first support ring of the support ring. The protrusions of eachof the second support rings have respective thicknesses that allow thedistance between the substrate held by the first support ring and thesubstrate held by the second support ring to be maintained to apredetermined value. Each of the multi-plate units, therefore, has asimple structure capable of holding the two substrates under thecondition that the back surfaces of the two substrates face each other.

According to the present invention, the substrate holder holds thesubstrates arranged at predetermined vertical intervals under thecondition that the back surfaces of the substrates face upward, and eachof the single-plate units uses the support ring to hold the end portionof the substrate under the condition that the front surface of thesubstrate faces upward. The substrate holder uses the support rings tohold the single-plate units under the condition that the back surface ofeach of the substrates held by the substrate holder faces the backsurface of the substrate held by each of the single-plate units. Thefirst distance between the front surface of one of the first pair ofsubstrates that are vertically adjacent to each other and have therespective front surfaces facing each other and the back surface of theother of the first pair of substrates is larger than the distancebetween the front surface of one of the second pair of substrates thatare vertically adjacent to each other and have the respective backsurfaces facing each other and the back surface of the other of thesecond pair of substrates. The substrates do not stick to each other.The number of the substrates held by the substrate holder can thereforebe increased compared with the conventional techniques while theuniformity of the treatment is ensured.

According to the present invention, the substrate holder has theplurality of columns surrounding the circumferences of the substrates tobe treated. Each of the columns has the claws and the unit supportsections. The claws hold the substrates. The unit support sections holdthe single-plate units by means of the protrusions of the support rings.The substrate holder, therefore, has a simple structure capable ofholding the substrates under the condition that the back surfaces of twosubstrates adjacent to each other face each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view schematically showing a heattreatment apparatus according to a first embodiment of the presentinvention.

FIG. 2( a) is a plan view schematically showing an example of asubstrate holder.

FIG. 2( b) is a front view showing the substrate holder.

FIGS. 3( a) and 3(b) are diagrams each showing an action of thesubstrate holder.

FIGS. 4( a) to 4(c) are diagrams each showing an action of the substrateholder.

FIGS. 5( a) to 5(d) are diagrams each showing an action of the substrateholder.

FIGS. 6( a) to 6(c) are diagrams each showing an action of the substrateholder.

FIG. 7 is a front view schematically showing another example of thesubstrate holder.

FIG. 8 is a cross sectional view schematically showing an example of avertical movement mechanism.

FIG. 9 is a cross sectional view schematically showing another exampleof the vertical movement mechanism.

FIGS. 10( a) and 10(b) are plan views each schematically showing anotherexample of the substrate holder.

FIGS. 11( a) to 11(c) are diagrams each schematically showing anotherexample of the substrate holder.

FIGS. 12( a) and 12(b) are plan views each schematically showing thesubstrate holder shown in FIGS. 11( a) to 11(c).

FIG. 13 is a vertical cross sectional view showing a heat treatmentapparatus according to a second embodiment of the present invention.

FIGS. 14( a) to 14(d) are diagrams schematically showing an example inwhich two wafers are held by a support ring under the condition thatback surfaces of the wafers face each other.

FIG. 15 is a front view schematically showing the state of a boat inwhich pairs of wafers are held by support rings at a predeterminedvertical interval.

FIG. 16( a) is a perspective view schematically showing a support ring.

FIG. 16( b) is an enlarged perspective view showing a main part of thesupport ring.

FIGS. 17( a) to 17(d) are diagrams schematically showing another examplein which two wafers are held by the support ring under the conditionthat back surfaces of the wafers face each other.

FIG. 18 is a front view schematically showing the state of a boat inwhich pairs of wafers are held by support rings at a predeterminedvertical interval.

FIGS. 19( a) and 19(b) are diagrams schematically showing anotherexample in which a wafer is held by a support ring.

FIGS. 20( a) and 20(b) are front views each schematically showing thestate of a boat in which each wafer having a back surface facing upwardis directly held by the boat, and each wafer having a front surfacefacing upward is held by the boat by means of a support ring.

FIG. 21( a) is a perspective view schematically showing the entiresupport ring.

FIG. 21( b) is an enlarged perspective view showing a main part of thesupport ring.

FIG. 22 is a perspective view schematically showing an example of theboat.

FIG. 23 is an enlarged view showing the boat shown in FIG. 22.

FIG. 24 is a plan view schematically showing the state of a support ringholding a wafer in the boat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

The best mode for carrying out the invention will be described belowwith reference to the accompanying drawings. FIG. 1 is a vertical crosssectional view schematically showing a heat treatment apparatusaccording to a first embodiment of the present invention. FIGS. 2( a)and 2(b) are respectively a plan view and a front view thatschematically show an example of a substrate holder.

In FIG. 1, reference numeral 1 denotes a heat treatment apparatus. Theheat treatment apparatus 1 has a housing 2 forming a framework. Avertical heat treating furnace 3 is provided inside and on the upperside of the housing 2. The vertical heat treating furnace 3 accommodatesmultiple substrates to be treated, e.g., semiconductor wafers w eachhaving a thin circular shape. In the vertical heat treating furnace 3, apredetermined treatment such as chemical vapor deposition (CVD) isperformed on the substrates. The heat treatment furnace 3 includes areaction tube 5, a lid 6 and a heater (heating device) 7. The reactiontube 5 is a vertical treatment container and made of quartz. Thereaction tube 5 has a furnace throat 4 at the bottom thereof. Thefurnace throat 4 has an opening. The lid 6 is capable of moving up anddown to close and open the furnace throat 4 of the reaction tube 5. Theheater 7 surrounds the circumference of the reaction tube 5 and iscapable of controlling the temperature of the inside of the reactiontube 5 to increase the temperature to a predetermined temperature, e.g.,a temperature ranging from 300° C. to 1200° C.

The reaction tube 5 and the heater 7 constitute the heat treatmentfurnace 3. A stainless steel (SUS) base plate 8 is horizontally orientedand mounts the reaction tube 5 and the heater 7. The base plate 8 islocated in the housing 2 and has an opening (not shown) to insert thereaction tube 5 into the heat treating furnace 3 from the bottom side ofthe heat treatment furnace 3 toward the top side thereof.

The reaction tube 5 has an outward protruding flange at a bottom edgeportion thereof. The flange is held by the base plate 8 by means of aflange support member. Accordingly, the reaction tube 5 is inserted intothe opening of the base plate 8 from the bottom side of the heattreating furnace 3 toward the top side thereof and installed in the heattreating furnace 3. The reaction tube 5 is removable from the bottomside to clean the reaction tube 5. The reaction tube 5 is connected to aplurality of gas introduction tubes and a discharge tube. The gasintroduction tubes introduce a process gas, an inert gas for purge, andthe like into the reaction tube 5. The discharge tube has a vacuum pump,a pressure control valve, and the like, which are capable of controllingthe pressure of a gas present in the reaction tube 5 to reduce thepressure. A cylindrical manifold may be connected to the bottom edgeportion of the reaction tube 5. In this case, the manifold forms afurnace throat; the manifold has gas introduction ports and a dischargeport; the introduction ports connect the gas introduction tubes and thereaction tube 5; and the discharge port connects the discharge tube andthe reaction tube 5.

A loading area (operation area) 11 is provided under the base plate 8that is located in the housing 2. In the loading area 11, wafers w aretransferred and held by a boat (substrate holder) 10. The boat 10 iscarried (loaded) into and carried (unloaded) out of the heat treatingfurnace 3 (i.e., the reaction tube 5). The boat 10 is provided on athermal insulation tube 13 that is located above the lid 6. An elevationmechanism 12 (refer to FIG. 11( a)) is provided in the loading area 11.The elevation mechanism 12 lifts and lowers the lid 6 to carry the boat10 into and out of the heat treating furnace 3.

The lid 6 is configured to come into contact with an edge of the furnacethroat 4 and close the furnace throat 4. The thermal insulation tube 13serves as furnace throat heat insulating means and prevents heat frombeing released from the furnace throat 4. The boat 10 is provided on thethermal insulation tube 13 that is located above the lid 6. A rotatingtable (not shown) is provided on the lid 6. The thermal insulation tube13 is located on the rotating table. A boat rotating mechanism 14 isprovided under the lid 6 and adapted to rotate the rotating table.

A load table (load port) 16 is provided on the front side of the housing2. The load table 16 mounts a container 15 thereon to carry thecontainer 15 into and out of the housing 2. The container 15 is capableof accommodating multiple wafers, e.g., 25 wafers at a predeterminedinterval. The container 15 has a removable lid (not shown) at the frontthereof and is an encapsulated container (also called a hoop). A doormechanism 17 is provided on the front and back of the loading area 11.The door mechanism 17 allows the inside of the container 15 and theinside of the loading area 11 to communicate with each other. In thiscase, the lid of the container 15 is removed. A transfer mechanism 20 isprovided in the loading area 11. The transfer mechanism 20 has aplurality of forks (transfer plates) 18 arranged at a predeterminedvertical interval. The forks 18 are used to transfer the wafers wbetween the container 15 and the boat 10.

A storage shelf unit 21 and a carrying mechanism (not shown) areprovided outside and above the front side of the loading area 11. Thestorage shelf unit 21 stores the container 15. The carrying mechanism isoperable to carry the container 15 from the load table 16 to the storageshelf unit 21 or vice versa. A shutter mechanism 22 is provided abovethe loading area 11. The shutter mechanism 22 covers (or closes) thefurnace throat 4 to suppress or prevent the release of a gas having ahigh temperature from the furnace throat 4 to the loading area 11 whenthe lid 6 is opened. An array device (aligner) 23 is provided under theload table 16. The array device 23 aligns a cutout portion (e.g., anotch) provided on the circumference of the wafer w (transferred by thetransfer mechanism 20) in a single direction.

The transfer mechanism 20 has a plurality of the transfer plates (forks)18 that hold respective horizontally-oriented wafers w arranged at apredetermined vertical interval. For example, five transfer plates 18hold five wafers w. In this case, the fork placed at the center of theforks is capable of independently advancing toward and retreating fromthe front side of the heat treatment apparatus. A pitch changingmechanism is operable to lift and lower the other forks (the first,second, fourth and fifth forks) in a non-step manner in order to changethe pitch of the forks on the basis of the central fork. The pitchchanging mechanism allows multiple wafers to be simultaneouslytransferred between the container 15 and the boat 10 since the pitch ofthe wafers arranged in the container 15 may be different from the pitchof the wafers arranged in the boat 10.

The transfer mechanism 20 has a stage 24 capable of moving up and downand revolving. Specifically, the transfer mechanism 20 has an elevationarm capable of moving up and down by means of a ball screw or the like.The box-shaped stage 24 is capable of horizontally revolving and placedon the elevation arm 25. A first movable body 26 is provided on thestage 24. A second movable body 27 is provided on the first movable body26. The first movable body 26 allows the central fork to move toward thefront side of the heat treatment apparatus. The second movable body 27allows the two forks located under the central fork and the two forkslocated above the central fork to move toward the front side of the heattreatment apparatus. The first and second movable bodies 26 and 27 canadvance and retreat in the longitudinal direction of thehorizontally-oriented stage 24.

A chucking mechanism may be provided at a base portion of each of theforks 18 of the transfer mechanism 20. The chucking mechanism is capableof gripping, from front and back sides of the fork 18 in thelongitudinal direction of the fork 18, the wafer w at a region betweenthe base portion of the fork 18 and a positioning groove located at anend portion of the fork 18. Each of the forks 18 of the transfermechanism 20 may have a normal transfer mode and a special transfer modeand is selectively operated according to one of the modes. In the normaltransfer mode, the fork 18 holds or grips the wafer w from the lowerside of the wafer w to transfer the wafer w. In the special transfermode, the fork 18 holds or grips the wafer w from the upper side of thewafer w to transfer the wafer w. A mapping sensor may be provided at theend portion of each of the forks 18. The mapping sensor detects theposition of the wafer in the boat 10 or the position of the wafer in thecontainer 15 to perform mapping.

The boat 10 is made of quartz, for example. The boat 10 is designed tohold horizontally-oriented wafers w that have large diameters, e.g.,diameters of 300 mm and are arranged at predetermined vertical intervals(pitches). Specifically, the boat 10 has two boat constituting bodies(holder constituents) 10 a and 10 b as shown in FIGS. 2( a) and 2(b).Each of the boat constituting bodies 10 a and 10 b has a plurality of,e.g., three columns 28. Each of the columns 28 has claws (protrusions)30 arranged at a predetermined vertical interval. Each of the claws 30serves as a substrate holding section for holding the circumference(circumferential portion) of the wafer w. The claws 30 are arranged at apredetermined vertical interval. The columns 28 are arranged on thecircumference of the same imaginary circle (or substantially the sameimaginary circle). Each of the boat constituting bodies 10 a and 10 b iscomposed of a top member 31, a bottom member 32 and the three columns28. Each of the top and bottom members 31 and 32 has a substantial Tshape. The top member 31 is paired with the bottom member 32 andseparated from the bottom member 32 in the vertical direction. The threecolumns 28 are fixed to respective end portions of the top member 31 andrespective end portions of the bottom member 32. The wafers are carriedinto and out of the boat 10 from a large space (wafer transfer space)between two of the three columns 28. In this case, the large spacebetween the two columns 28 is largest among spaces between any two ofthe three columns 28. The positions of the boat constituting bodies 10 aand 10 b can be changed relative to each other in the vertical direction(the difference between the vertical positions of the boat constitutingbodies 10 a and 10 b can be changed) under the condition that thecolumns 28 of the boat constituting body 10 a are close to therespective corresponding columns 28 of the boat constituting body 10 bon the circumference of the same imaginary circle, as shown in FIGS. 2(a) and 2(b). In this case, it is preferable that the boat constitutingbody 10 a be fixed and the boat constituting body 10 b be movable, tosimplify the structure of a vertical movement mechanism.

The pitch of the claws 30 of the boat constituting body 10 a is the sameas the pitch of the claws 30 of the boat constituting body 10 b. Asshown in FIGS. 4( a) to 6, the wafers with the front surfaces facingupward is held by the boat constituting body 10 a, while the wafers withthe back surfaces facing downward is held by the boat constituting body10 b. The wafer with the front surface facing upward and the wafer withthe back surface facing upward are alternately arranged in the verticaldirection. The positions of the boat constituting bodies 10 a and 10 bcan be changed relative to each other in the vertical direction underthe condition that a distance pa between the front surface of one of afirst pair of wafers that are vertically adjacent to each other and havethe respective front surfaces facing each other and the back surface ofthe other of the first pair of wafers is set to ensure uniformity of thetreatment and larger than a distance pb between the front surface of oneof a second pair of wafers that are vertically adjacent to each otherand have the respective back surfaces facing each other and the backsurface of the other of the second pair of wafers. In this case, it ispreferable that the boat constituting body 10 a be larger than (longerin the vertical direction than) the boat constituting body 10 b for anoperation of moving at least one of the boat constituting bodies 10 aand 10 b to change the vertical positions of the boat constitutingbodies 10 a and 10 b relative to each other (FIG. 2( b)). In this case,the distance pa is between one of the first pair of wafers and the otherof the first pair of wafers, while the distance pb is between one of thesecond pair of wafers and the other of the second pair of wafers.

In FIGS. 4( a) to 5(d), the boat constituting bodies 10 a and 10 b areset such that each distance between the claw 30 of the boat constitutingbody 10 a and the claw 30 (located directly under the claw 30 of theboat constituting body 10 a) of the boat constituting body 10 b is setto be small in advance. As shown in FIGS. 4( a) and 5(a), a wafer isfirst transferred onto the claws 30 of the boat constituting body 10 aunder the condition that the wafer with the front surface wa facingupward is held or gripped by the fork 18 from the lower side of thewafer. Next, the boat constituting body 10 b moves down as shown in FIG.5( b). Then, a wafer is transferred onto the claws 30 of the boatconstituting bodies 10 b under the condition that wafer with the backsurface wb facing upward is gripped by the fork 18 from the upper sideof the wafer, as shown in FIGS. 4(b) and 5( c). The boat constitutingbody 10 b moves up to returns to the original position as shown in FIG.4( c) and FIG. 5( d). Therefore, the distance pa is set such that theuniformity of the treatment is ensured, and the distance pb is smallerthan the distance pa.

In FIGS. 6( a) to 6(c), the boat constituting bodies 10 a and 10 b areset such that a distance between one of the claws 30 of the boatconstituting body 10 a and the claw 30 (located directly under the oneof the claws 30 of the boat constituting body 10 a) of the boatconstituting body 10 b is set to be equal to a distance between anotherone of the claws 30 of the boat constituting body 10 a and the claw 30(located directly under the other of the claws 30 of the boatconstituting body 10 a) of the boat constituting body 10 b. As shown inFIG. 6( a), a wafer is first transferred onto the claws 30 of the boatconstituting body 10 a under the condition that the wafer with the frontsurface wa facing upward is held or gripped by the fork 18 from thelower side of the wafer. Next, a wafer is transferred onto the claws 30of the boat constituting body 10 b under the condition that the waferwith the back surface wb facing upward is held or gripped by the fork 18from the lower side of the wafer, as shown in FIG. 6( b). Then, the boatconstituting body 10 a moves up as shown in FIG. 6( c) such that theclaws 30 of the boat constituting body 10 b are close to back surfacesof the claws 30 of the boat constituting body 10 a. Therefore, thedistance pa is set to ensure the uniformity of the treatment, and thedistance pb is smaller than the distance pa.

In this case, the total of the thickness ta of the wafer, the thicknesstb of the fork, and clearances sa and sb for placement is equal to aplacement pitch pt (of the wafers), as shown in FIG. 3( a). Theplacement pitch pt is equal to a half of a boat pitch P (equal to thepitch of the claws of one of the boat constituting bodies). The distancepb is slightly larger than the sum of the thickness tc of the claw andthe thickness ta of the wafer w. The distance pa is equal to a valueobtained by subtracting the distance pb from the boat pitch R Comparedwith an existing system (having 8 placement pitches and 61 slots), whenthe placement pitch pt is 7 mm, the number of slots is 7×70. Thisresults in the fact that nine wafers can be added. When the placementpitch pt is 5.6 mm, the number of slots is 5.6×87. This results in thefact that twenty six wafers (that can be accommodated in one container)can be added. A vertical movement mechanism 33 (described later) iscapable of changing the positions of the boat constituting bodies 10 aand 10 b relative to each other to change the distance pa. The pitch pacan be in the range from approximately 0 mm (e.g., the thicknesses ofthe claws are approximately 2 mm) to more than 10 mm (e.g., toapproximately 11 mm). The distance pb can be also changed in the samemanner.

The positions of the boat constituting bodies 10 a and 10 b can bechanged relative to each other in the vertical direction by means of thevertical movement mechanism 33. In the present embodiment, the boatconstituting body 10 a is fixed to and placed on a rotating table 34(refer to FIG. 8) that is provided on the lid 6, and the boatconstituting body 10 b is moved up and down by the vertical movementmechanism 33. The vertical movement mechanism 33 is attached to the boatrotating mechanism 14 that is provided under the lid 6.

The boat rotating mechanism 14 has a cylindrical sleeve 35, a rotatingbody 37, a hollow rotating shaft 38 and a motor (not shown). The sleeve35 is fixed to a central axis portion of the lid 6. The rotating body 37is provided around the circumference of the sleeve 35 via a ball bearing36. The rotating body 37 is rotatable. The rotating shaft 38 is fixed toa lower central portion of the rotating body 37. In addition, therotating shaft 38 extends in the sleeve 35 and through the upper surfaceof the lid 6, and is coupled with the rotating table 34 that is providedon the lid 6. The motor drives the rotating body 37 by means of anendless belt wound around the circumference of the rotating body 37 tocause the rotating body 37 to rotate.

The vertical movement mechanism 33 has an elevation shaft (verticalmovement shaft) 40 and an elevation drive section 41. The elevationshaft 40 extends through the rotating shaft 38 of the rotating mechanism14 and is capable of moving up and down. The elevation drive section 41causes the elevation shaft 40 to move up and down. The vertical movementmechanism 33 also has a disk-shaped vertically movable body 43 that isprovided under the rotating body 37 and held by a guide 42. Thevertically movable body 43 is capable of moving up and down. Theelevation shaft 40 is erected on a central portion of the verticallymovable body 43. In addition, the elevation shaft 40 extends through ahollow portion (shaft hole) 38 a of the rotating shaft 38 and projectsout of the upper surface of the lid 6. The elevation drive section 41may be an air cylinder. A bellows 44 is preferably provided between therotating body 37 and the vertically movable body 43 to maintainair-tightness of a through-hole section of the elevation shaft 40. Theelevation shaft 40 also extends through the rotating table 34 and thethermal insulation tube 13 and is coupled with the bottom member 32 (notshown in FIG. 8) of the boat constituting body 10 b.

According to the heat treatment method and the heat treatment apparatusas described above, the boat 10 is composed of the two holderconstituents 10 a and 10 b. Each of the holder constituents has theplurality of columns arranged on the circumference of the same imaginarycircle. Each of the columns has the claws 30 arranged at a predeterminedvertical interval. Each of the claws holds the edge portion of thewafer. The boat constituting body 10 a holds the wafers w with the frontsurfaces wa facing upward, while the boat constituting body 10 b holdsthe wafers w with the back surfaces facing upward. After the wafers areheld by the boat constituting bodies 10 a and 10 b, at least one of thetwo holder constituents 10 a and 10 b moves in the vertical direction tochange the positions of the two holder constituents 10 a and 10 brelative to each other. Accordingly, the wafer with the front surfacefacing upward and the wafer with the back surface facing upward arealternately arranged in the vertical direction. Therefore, the distancepa is set to ensure the uniformity of the treatment, and the distance pbis smaller than the distance pa. This makes it possible that the numberof wafers to be held by the boat 10 is increased compared with theconventional techniques while the uniformity of the treatment isensured, and the throughput can be improved. Even when the distance pais increased and the number of wafers to be held by the substrate holderis the same as that of wafers in the conventional techniques, it ispossible to improve the uniformity of the treatment while the number ofwafers to be held by the substrate holder is maintained.

FIG. 7 is a front view schematically showing another example of theboat. The boat shown in FIG. 7 is different from the boat describedabove. The boat shown in FIG. 7 is not composed of the two boatconstituting bodies and has a plurality of, for example, three columns28. Each of the columns 28 has claws 30 on which wafers are placed. Inthe boat shown in FIG. 7, the wafer with the front surface facing upwardand the wafer with the back surface facing upward are alternatelyarranged in the vertical direction. The distance pa is set to ensure theuniformity of the treatment, while the distance pb is smaller than thedistance pa. According to the present embodiment, it is possible toensure uniformity of the treatment with a simple structure of thesubstrate holder and increase the number of wafers to be held by thesubstrate holder compared with conventional techniques. Even when thedistance pa is increased and the number of wafers to be held by thesubstrate holder is the same as that of wafers in the conventionaltechniques, it is possible to improve the uniformity of the treatmentwhile the number of wafers to be held by the substrate holder ismaintained.

FIG. 10 is a plan view schematically showing another example of thesubstrate holder. In the boat 10 according to the present embodiment, atleast one of the boat constituting bodies 10 a and 10 b is pivoted inthe circumferential direction by a pivoting mechanism 45 (describedlater) to change the positions relative to each other in order that thecolumns 28 surround the end portions of the wafers under the conditionthat the distances between any two of the columns 28 is smaller than thediameters of the wafers. This configuration of the boat 10 prevents thewafers from sliding and falling out of the boat 10. In this case, it ispreferable that the boat constituting body 10 b be pivoted by apredetermined angle θ (e.g., θ=60 to 90 degrees) with respect to theboat constituting body 10 a to change the positions of the boatconstituting body 10 a and 10 b relative to each other.

The pivoting mechanism 45 has a configuration shown in FIG. 9, forexample. The elevation shaft 40 (refer to FIG. 8) is rotatableindependently of the rotating shaft 38. A second rotating body 46 istherefore provided under the rotating body 37 of the rotating mechanism14 and held by the guide 42 and the bellows 44. The second rotating body46 is capable of moving up and down. The elevation shaft 40 has arotatable base portion 40 a provided in the second rotating body 46. Thebase portion 40 a is held by a ball bearing 47. A motor (not shown) isprovided under the second rotating body 46 and causes the elevationshaft 40 to rotate. The elevation drive section, such as an aircylinder, causes the elevation shaft 40 and the second rotating body 46to move up and down. Accordingly, the elevation shaft 40 is capable ofnot only moving up and down but also pivoting. The pivoting of theelevation shaft 40 allows the boat constituting body 10 b to pivot tochange the position of the boat constituting body 10 b relative to theposition of the boat constituting body 10 a.

FIGS. 11( a)-11(c) are diagrams schematically showing another example ofthe substrate holder. FIGS. 12( a) and 12(b) are plan viewsschematically showing the substrate holder shown in FIG. 11( a)-11(c).In the present embodiment, the vertical movement mechanism 33 causes theboat constituting body 10 b to move relative to the boat constitutingbody 10 a. The vertical movement mechanism 33 has the elevationmechanism 12 and a latch mechanism 48. The elevation mechanism 12 isdesigned to move up and down the boat 10 to carry the boat 10 into andout of the heat treating furnace. The boat 10 is located on the thermalinsulation tube 13 present above the lid 6 (for closing the furnacethroat of the heat treating furnace). The latch mechanism 48 is designedto latch the boat constituting body 10 b before the boat reaches itsstop position when the boat is carried out of the heat treating furnaceby the elevation mechanism 12 and restore the relationship between thevertical positions of the holder constituting body 10 a and 10 brelative to each other.

In this case, the pivoting mechanism 45 for pivoting the boatconstituting body 10 b relative to the boat constituting body 10 a isprovided with the latch mechanism 48 and the boat rotating mechanism 14.The boat rotating mechanism 14 pivots the boat constituting body 10 a bya predetermined angle θ relative to the boat constituting body 10 b inthe circumferential direction to change the position of the boatconstituting body 10 a relative to the position of the boat constitutingbody 10 b latched by the latch mechanism 48.

The latch mechanism 48 has a plurality of, e.g., three latch members 48a and an advance/retreat drive section (not shown). The latch members 48a latch (hold) the lower surface of the boat constituting body 10 a,e.g., each end portion (corresponding to a lower end portion of eachcolumn 28) of the bottom member 32. The advance/retreat drive sectionmoves the latch members 48 outward with respect to the boat 10 in theradial direction of the boat 10 and moves the latch members 48 a inwardwith respect to the boat 10 in the radial direction of the boat 10 toavoid interference with lid 6 during the vertical movement of the lid 6.The advance/retreat drive section may be an air cylinder.

The wafers are carried into the boat 10 in the state shown in FIGS. 11(a) and 12(a). In this case, the boat constituting bodies 10 a and 10 bare in the state in which the columns 28 of the boat constituting body10 a are respectively close to the corresponding columns 28 of the boatconstituting body 10 b and in which the boat constituting body 10 b islatched by the latch members 48 at a position higher than the positionof the boat constituting body 10 a. After the wafers are held by theboat 10, the boat constituting body 10 a is in the state shown in FIG.11( a). The boat constituting body 10 a is then rotated by thepredetermined angle θ by the boat rotating mechanism 14. Then, distancesbetween any two of the columns 28 of the boat constituting bodies 10 aand 10 b are set to be smaller than the diameters of the wafers in orderthat the columns 28 surround the end portions of the wafers. Thisprevents the wafers from sliding and falling out of the boat during thecarrying of the wafers into and out of the boat and during the heattreatment.

Next, after the elevation mechanism 12 lifts the lid 6 to carry the boat10 into the heat treating furnace, the furnace throat of the heattreating furnace is closed by means of the lid 6. In the process oflifting the lid 6, the boat constituting body 10 a is first moved to aposition higher by a predetermined distance than the boat constitutingbody 10 b (the positions of the boat constituting bodies 10 a and 10 bare changed relative to each other). The state (in which the distancebetween the front surface of one of the first pair of wafers that arevertically adjacent to each other and have the respective front surfacesfacing each other and the back surface of the other of the first pair ofwafers is larger than the distance between the front surface of one ofthe second pair of wafers that are vertically adjacent to each other andhave the respective back surfaces facing each other and the back surfaceof the other of the second pair of wafers) shown in FIGS. 4( c) and 6(c)is then obtained. In the process of lifting the lid 6, the latch members48 a of the latch mechanism 48 are moved (retreated) outward withrespect to the boat 10 in the radial direction of the boat 10 to avoidinterference with the lid 6, as shown in FIG. 11( c). In order to carrythe boat 10 out of the heat treating furnace, the operations shown inFIGS. 11( a) to 11(c) are performed in the opposite order, that is, inthe order of the operation shown in FIG. 11C, the operation shown inFIG. 11B, and the operation shown in FIG. 11A. The substrate holdershown in FIGS. 11A to 11C can obtain a similar effect to the otherexample of the substrate holder.

Although the first embodiment of the present invention is describedabove with reference to the drawings, the heat treatment method and theheat treatment apparatus are not limited to first embodiment and may bemodified without departing from the scope and sprit of the presentinvention.

Second Embodiment

The best mode for carrying out the invention will be described belowwith reference to the accompanying drawings. FIG. 13 is a vertical crosssectional view schematically showing a heat treatment apparatusaccording to a second embodiment of the present invention. FIGS. 14( a)to 14(d) are diagrams schematically showing an example in which twowafers are held by means of a support ring under the condition that theback surfaces of the adjacent wafers face each other. FIG. 15 is a frontview schematically showing a boat in which pairs of wafers held by meansof the support rings are hold at predetermined vertical intervals. FIG.16( a) is a perspective view schematically showing the support ring, andFIG. 16( b) is an enlarged perspective view showing a main portion ofthe support ring.

In FIG. 13, reference numeral 101 denotes the vertical heat treatmentapparatus. The heat treatment apparatus 101 has a housing 102 forming aframework. A heat treatment furnace 103 is provided inside and on theupper side of the housing 102. The heat treatment furnace 103accommodates a plurality of substrates to be treated, e.g., thincircular semiconductor wafers w. In the heat treatment furnace 103, apredetermined treatment such as chemical vapor deposition (CVD) isperformed on the substrates. The heat treatment furnace 103 is mainlycomposed of a reaction tube 105, a lid 106 and a heater (heating device)107. The reaction tube 105 is a vertical treatment container and made ofquartz. The reaction tube 105 has a furnace throat 104 at the bottomthereof. The furnace throat 104 has an opening. The lid 106 is capableof moving up and down to close and open the furnace throat 104 of thereaction tube 105. The heater 107 surrounds the circumference of thereaction tube 105 and is capable of controlling the temperature of theinside of the reaction tube 105 to increase the temperature to apredetermined temperature, e.g., a temperature ranging from 300° C. to1200° C.

The reaction tube 105 and the heater 107 constitute the heat treatmentfurnace 103. A stainless steel (SUS) base plate 108 is horizontallyoriented and mounts the reaction tube 105 and the heater 107. The baseplate 108 is located in the housing 102 and has an opening (not shown)to insert the reaction tube 105 into the heat treating furnace 103 fromthe bottom side of the heat treatment furnace 103 to the top sidethereof.

The reaction tube 105 has an outward protruding flange at a bottom edgeportion thereof. The flange is held by the base plate 108 by means of aflange support member. Accordingly, the reaction tube 105 is insertedinto the opening of the base plate 108 from the bottom side of the heattreating furnace 103 to the top side and installed in the heat treatingfurnace 103. The reaction tube 105 is removable from the base plate 108downwardly to be cleaned. The reaction tube 105 is connected to aplurality of gas introduction tubes and a discharge tube. The gasintroduction tubes introduce a process gas, an inert gas for purge, andthe like into the reaction tube 105. The discharge tube has a vacuumpump, a pressure control valve, and the like, which are capable ofcontrolling the pressure of a gas present in the reaction tube 105 to bereduced. A cylindrical manifold may be connected to the bottom edgeportion of the reaction tube 105. In this case, the manifold forms afurnace throat; the manifold has gas introduction ports and a dischargeport; the introduction ports connect the gas introduction tubes and thereaction tube 105; and the discharge port connects the discharge tubeand the reaction tube 105.

A loading area (operation area) 112 is provided under the base plate 108that is located in the housing 102. In the loading area 112, a boat(substrate holder) 111 is carried (loaded) into and carried (unloaded)out of the heat treating furnace 103 (i.e., the reaction tube 105); andwafers w are held by the boat 111. The boat 111 is provided on a thermalinsulation tube 110 that serves as furnace throat heat insulating meansand is located above the lid 106. An elevation mechanism (not shown) isprovided in the loading area 112. The elevation mechanism causes the lid106 to move up and down to carry the boat 111 into and out of the heattreating furnace 103.

The lid 106 is configured to come into contact with an edge of thefurnace throat 104 and close the furnace throat 104. A rotatingmechanism 113 is attached to a lower portion of the lid 106 and rotatesthe boat 111. The rotating mechanism 113 has a rotating shaft extendingthrough the lid 106 in an airtight manner. The rotating shaft of therotating mechanism 113 rotates a rotating table (not shown) or a supportleg 130 (shown in FIG. 22). The rotating table is provided on the lid106. The support leg 130 is provided at a central bottom portion of theboat 111.

A load table (load port) 115 is provided on the front side of thehousing 102. The load table 115 mounts a container 114 thereon to carrythe container 114 into and out of the housing 102. The container 114 iscapable of accommodating multiple wafers, e.g., 25 wafers at apredetermined interval. The container 114 has a removable lid (notshown) at the front thereof and is an encapsulated container (alsocalled a hoop). A door mechanism 116 is provided on the front and backof the loading area 112. The door mechanism 116 allows the inside of thecontainer 114 and the inside of the loading area 112 to communicate witheach other. In this case, the lid of the container 114 is removed. Atransfer mechanism 118 is provided in the loading area 112. The transfermechanism 118 has a plurality of horizontally-oriented forks (transferplates) 117 arranged at a predetermined vertical interval. The forks 117are used to transfer the wafers w between the container 114 and the boat111.

A storage shelf unit 120 and a carrying mechanism (not shown) areprovided outside and above the front side of the loading area 112. Thestorage shelf unit 120 stores the container 114. The carrying mechanismis operable to carry the container 114 from the load table 115 to thestorage shelf unit 120 or vice versa. A shutter mechanism 121 isprovided above the loading area 112. The shutter mechanism 121 covers(or closes) the furnace throat 104 to suppress or prevent the release ofa gas having a high temperature from the furnace throat 104 to theloading area 112 when the lid 106 is opened. An array device (aligner)122 is provided under the load table 115. The array device 122 aligns acutout portion (e.g., a notch) provided on the circumference of thewafer w (transferred by the transfer mechanism 118) in a singledirection.

The fork 117 placed at the center of the forks 117 is capable ofadvancing toward and retreating from the front side of the heattreatment apparatus. A pitch changing mechanism is operable to lift andlower the other forks (the first, second, fourth and fifth forks) in anon-step manner in order to change the pitch of the forks on the basisof the central fork. The pitch changing mechanism allows multiple wafersto be simultaneously transferred between the container 114 and the boat111 since the pitch of the wafers arranged in the container 114 may bedifferent from the pitch of the wafers arranged in the boat 111.

The transfer mechanism 118 has a stage 123 capable of moving up and downand revolving. Specifically, the transfer mechanism 118 has an elevationarm 124 capable of moving up and down by means of a ball screw or thelike. The box-shaped stage 123 is capable of horizontally revolving andplaced on the elevation arm 124. A first movable body 125 is provided onthe stage 123. A second movable body 126 is provided on the firstmovable body 125. The first movable body 125 allows the central fork tomove in the longitudinal direction of the stage 123. The second movablebody 126 allows the two forks located under the central fork and the twoforks located above the central fork to move.

A chucking mechanism may be provided at a base portion of each of theforks 117 of the transfer mechanism 118. The chucking mechanism iscapable of gripping, from front and back sides of the fork 117 in thelongitudinal direction of the fork 117, the wafer w at a region betweenthe base portion of the fork 117 and a positioning groove located at anend portion of the fork 117. Each of the forks 117 of the transfermechanism 118 may have a normal transfer mode and a special transfermode and is selectively operated according to one of the modes. In thenormal transfer mode, the fork 117 holds or grips the wafer w from thelower side of the wafer w to transfer the wafer w. In the specialtransfer mode, the fork 117 holds or grips the wafer w from the upperside of the wafer w to transfer the wafer w. A mapping sensor may beprovided at the end portion of each of the forks 117. The mapping sensordetects the position of the wafer in the boat 111 or the position of thewafer in the container 114 to perform mapping.

The boat 111 is made of quartz, for example. The boat 111 is designed tohold horizontally-oriented wafers w that have large diameters, e.g.,diameters of 300 mm and are arranged at predetermined vertical intervals(pitches). As shown in FIG. 22, the boat 111 has a top plate 111 a, abottom plate 111 b and a plurality of, e.g., three columns 127. Thecolumns 127 are provided between the top plate 111 a and the bottomplate 111 b. An auxiliary column 128 may be provided if necessary, inaddition to the columns 127. The boat 111 has the support leg 130provided at the central bottom portion of the boat 111. The support leg130 is coupled with the rotating shaft of the rotating mechanism 113attached to the lower portion of the lid 106. In the case where the boat111 is used, a heat shield member (not shown) is provided between thelid 106 and the bottom plate 111 b in place of the thermal insulationtube. The boat 111 may not have the support leg and may have a thermalinsulation tube provided under the boat 111 (refer to FIG. 13). In thiscase, the thermal insulation tube is located on the rotating table thatis present on the lid 106.

As shown in FIGS. 14( a) to 15, the boat 111 holds a plurality ofmulti-plate units 132. In the multi-plate units 132, the circumferentialportions of two wafers are hold by means of the support rings 131 in thevertical direction such that the back surfaces of the wafers face eachother. A distance Pa′ (shown in FIG. 15) between the back surface of oneof the two wafers w held by the multi-plate unit 132 and the frontsurface of the other of the two wafers w is smaller than a distance Pb′(shown in FIG. 15) between upper surfaces of claws 133 (of the column127) vertically adjacent to each other. The support rings 131 are madeof quartz, for example. Each of the support rings 131 is composed of afirst support ring 131 a and a second support ring 131 b. The firstsupport ring 131 a holds the horizontally-oriented wafer w under thecondition that the back surface wb of the wafer w faces upward (thefront surface wa of the wafer w faces downward). The second support ring131 b is provided on the first support ring 131 a and holds thehorizontally-oriented wafer w under the condition that the front surfacewa of the wafer w faces upward.

Each of the first and second support rings 131 a and 131 b has acircular ring portion 131 x and a plurality of, e.g., four protrusions131 y. The circular ring portion 131 x has a diameter (outer diameter)that is the same as or slightly larger than that of the wafer. Theprotrusions 131 y protrude from the circumference of the circular ringportion 131 x and are arranged at an appropriate interval. In order toensure a large area (to be treated) of the front surface wa (facingdownward) of the wafer w placed on the circular ring portion 131 x ofthe first support ring 131 a, it is preferable that an inner diameter ofthe circular ring portion 131 x of the first support ring 131 a bemaximized to a value close to the diameter of the wafer w.

It is preferable that an upper surface of the circular ring portion 131x and upper surfaces of the protrusions 131 y be in the same plane. Theprotrusions 131 y may protrude from the upper surface of the circularring portion 131 x to prevent the wafer from sliding and falling out ofthe boat. The protrusions 131 y of the second support ring 131 b arelocated on the protrusions 131 y of the first support ring 131 a. Thethicknesses t of the protrusions 131 y of the second support ring 131 bare set such that the distance between the front surface of the waferplaced on the first support ring 131 a and the back surface of the waferplaced on the second support ring 131 b is maintained to thepredetermined distance Pa′.

In order to assemble the multi-plate unit 132, a wafer w is first placedon the upper surface of the circular ring portion 131 x of the firstsupport ring 131 a as shown in FIGS. 14( a) and 14(b). Next, the secondsupport ring 131 b is placed on the first support ring 131 a as shown inFIGS. 14( c) and 14(d). Then, another wafer w is placed on the uppersurface of the circular ring portion 131 x of the second support ring131 b. The abovementioned assembly operation may be performed in theheat treatment apparatus 1. Alternatively, the pre-assembled multi-plateunits 132 may be accommodated in the container 114.

Each of the columns 127 of the boat 111 has the claws 133 for holdingthe multi-plate units 132 at an interval (equal to the distance Pb′)that is larger than the distance Pa′ between the front surface of one ofthe two wafers w held by the multi-plate unit 132 and the back surfaceof the other of the two wafers w. That is, the protrusions 131 y of thefirst support ring 131 a of each multi-plate unit 132 are placed(latched) on upper surfaces of the claws 133 that hold the multi-plateunit 132. The distance (pitch) Pa′ between the front surface of one ofthe two wafers w held by the multi-plate unit 132 and the back surfaceof the other of the two wafers w is equal to, for example, 2 mm. Thedistance (pitch) Pb′ between the multi-plate units 132 held by the boat111 is equal to, for example, 11 mm. Accordingly, the number of wafersto be held by the boat 111 can be increased by 25 wafers that can beaccommodated in one container 114.

In the example of the drawings, the thicknesses of the protrusions 131 yof the first support ring 131 a are the same as those of the protrusions131 y of the second support ring 131 b. The thicknesses of theprotrusions 131 y of the first support ring 131 a may be the same asthat of the circular ring portion 131 x. The cross sections of theprotrusions 131 y are sufficiently smaller than those of the columns127. Thus, the protrusions 131 y do not have an impact on the wafers,unlike the columns 127 (that may have an impact on uniformity of thetreated surface of each of the wafers since a portion of the treatedsurface of the wafer, which is located around the end portion of thewafer, is disturbed by the columns 127). In addition, since thesupport-rings 131 are held by the claws 133 of the columns 127 by meansof the protrusions 131 y, the columns 127 are separated from the endportions of the wafers w. The end portions of the wafers w are placed onthe upper surfaces of the respective circular ring portions 131 x. It istherefore possible to perform the treatment uniformly on the surfaces ofthe wafers w including the end portions thereof in a similar manner tothat to be performed in a ring boat.

According to the heat treatment method and the heat treatment apparatus101 as described above, each of the multi-plate units 132 holds the endportions of two wafers by means of the support ring 131 in the boat 111.The wafers held by the multi-plate units 132 are arranged in thevertical direction. The distance Pb′ between the multi-plate units 132adjacent to each other is larger than the distance Pa′ between the backsurface of one of the two wafers held by the multi-plate unit 132 andthe back surface of the other of the two wafers. Accordingly, the waferwith the front surface facing upward and the wafer with the back surfacefacing upward are alternately arranged in the vertical direction. Thedistance Pa′ is smaller than the distance Pb′. Since the distance pa isset to ensure the uniformity of the treatment, and the distance pb issmaller than the distance pa, it is possible to increase the number ofwafers to be held by the boat compared with conventional techniques andensure the uniformity of the treatment. It is also possible to improve athroughput of the heat treatment apparatus. In addition, since each ofthe multi-plate units 132 holds end portions of two wafers with the backsurfaces facing each other by means of the support ring 131, the twowafers do not stick to each other. In addition, the multi-plate units132 can be accommodated in the container 114 one by one. Thus, twowafers can be transferred for each transfer operation. This operation isefficient and can reduce the time for transferring wafers. Also, thetransfer operation makes it possible to improve the throughput. In thiscase, the distance pa is between one of the first pair of wafers and theother of the first pair of wafers, while the distance pb is between oneof the second pair of wafers and the other of the second pair of wafers.

FIGS. 17( a) to 17(d) are diagrams schematically showing another examplein which two wafers are held by the support ring under the conditionthat the back surfaces of the wafers face each other. FIG. 18 is adiagram showing pairs of wafers are held by the support rings in theboat at predetermined vertical intervals. In this example, the firstsupport ring 131 a and the second support ring 131 b (that constitutethe support ring 131 forming the multi-plate unit 132) are placed upsidedown (facing the opposite direction compared with those shown in FIG.15). The lower surface of the circular ring portion 131 x and the lowersurfaces of the protrusions 131 y are in the same plane. The uppersurfaces of the protrusions 131 y are located at positions higher thanthat of the front surface of the wafer placed on the circular ringportion 131 x. In this case, the protrusions 131 y surround thecircumference of the wafer placed on the upper surface of the circularring portion 131 x to prevent the wafer from sliding and falling out ofthe boat. The boat having the configuration in this example can obtain asimilar effect to the boat according to the first embodiment.

FIGS. 19( a) and 19(b) are diagrams schematically showing anotherexample in which a single wafer is held by the support ring. FIGS. 20(a) and 20(b) are front views each schematically showing the case inwhich a wafer having a back surface facing upward is held directly bythe boat and a wafer having a front surface facing upward is held by theboat by means of the support ring. In this example, the boat 111 holdsthe wafer w with the back surface wb facing upward and a single-plateunit 135 that are alternately arranged at a predetermined verticalinterval. The single-plate unit 135 is configured to hold the endportion of the wafer w by means of the support ring 134 under thecondition that the front surface wa of the wafer w faces upward. In thiscase, the back surface of the wafer w directly held by the boat 111 andthe back surface of the wafer w held by the single-plate unit 135 faceeach other. A distance Pa between the back surface of a wafer held bythe single-plate unit 135 and the front surface of a wafer that is heldby the claws 136 and located directly under the wafer held by thesingle-plate unit 135 is smaller than a distance Pb between the frontsurfaces of the wafers held by the claws vertically adjacent to eachother.

The single-plate unit 135 is configured to hold the wafer w on the uppersurface of the support ring 134 under the condition that the frontsurface wa (to be treated) of the wafer faces upward, as shown in FIG.19( b). The support ring 134 has a circular ring portion 134 x and aplurality of, for example, four protrusions 134 y. The circular ringportion 134 x has a diameter (outer diameter) that is the same as orslightly larger than the diameter of the wafer. The protrusions 134 yprotrude from the circumference of the circular ring portion 134 x andare arranged at an appropriate interval. The thickness of the circularring portion 134 x is small, for example, 2.5 mm. The thickness of thecircular ring portion 134 x is the same as the thicknesses of theprotrusions 134 y. The circular ring portion 134 x has an inner diameterthat is not specified.

The single-plate unit 135 is assembled only by placing the wafer w on anupper surface of the circular ring portion 134 x of the support ring 134as shown in FIGS. 19( a) and 19(b). The single-plate unit 135 may beassembled in the heat treatment apparatus. Alternatively, thepre-assembled single-plate unit 135 may be accommodated in the container114. In this case, as the container 114, a first container foraccommodating wafers w and a second container for accommodating thesingle-plate unit 135 are used.

As shown in FIGS. 22 to 24, the boat 111 has the plurality of, forexample, three columns 127 surrounding the end portions of the wafers.Each of the columns 127 has claws 136 and unit support sections 137. Theclaws 136 hold the wafers w. The unit support sections 137 hold thesingle-plate units 135 by means of the protrusions 134 y of the supportrings 134. The boat 111 shown in FIGS. 22 and 24 has a top plate 111 a,a bottom plate 111 b, the plurality of, e.g., three columns 127 and twoauxiliary columns 128. The columns 127 and the auxiliary columns 128 areprovided between the top plate 111 a and the bottom plate 111 b. Thewafer w or the single-plate unit 135 is carried into (held by) the boat111 from the right side of FIG. 24.

An imaginary line connecting between two of the columns 127 isperpendicular to the direction (left-right direction of FIG. 24) inwhich the wafer w is transferred and carried into the boat. The otherone of the columns 127 is located on the side opposite to the side onwhich the wafer w is carried into the boat. Also, the other one of thecolumns 127 is located on an imaginary line that extends through thecenter of the wafer and is parallel to the direction in which the waferw is transferred and carried into the boat. Each of the three columns127 has the claws 136 at a predetermined vertical interval (pitch) PC.The claws hold the end portions of the wafers w. The followingexpression is established: Pc=Pa′+Pb′.

As the unit support section 137, flat arc front-side unit supportsections 137 a and a back-side unit support section 137 b are provided.The front-side unit support sections 137 a extend from the respectivecolumns 127 that are located on the left and right sides with respect tothe imaginary line that extends through the center of the wafer and isparallel to the direction in which the wafer w is carried into the boat.The front-side unit support sections 137 a extend to the front side(right side of FIG. 24) and along the support ring 134. In addition, thefront-side unit support sections 137 a receive (hold) the respectiveprotrusions 134 y located on the front side of the support ring 134. Aflat arc-shaped support plate 138 may be provided as the back-side unitsupport section 137 b. In this case, the support plate 138 extends fromone of the pair of auxiliary columns 128 through the columns 127 locatedon the back side to the other of the pair of auxiliary columns 128.

In the present embodiment, the wafers w are subsequently placed on theclaws 136 of the boat 111 by the transfer mechanism 118 such that thefront surfaces of the wafers w face upward, as shown in FIG. 20A. Afterthat, the single-plate units 135 are held by the unit support sections137 by means of the protrusions 134 y. According to the presentembodiment, the wafers w do not stick to each other. In addition, thenumber of wafers to be held by the boat 111 is increased compared withthe conventional techniques while the uniformity of the treatment isensured.

Although the embodiments of the present invention are described above,the present invention is not limited to the abovementioned embodimentsand may be modified without departing the scope and spirit of thepresent invention.

1. A heat treatment method, in which a plurality of substrates to betreated is held by a substrate holder at predetermined verticalintervals, the substrate holder is carried into a heat treating furnace,and a predetermined heat treatment is performed on the substrates,comprising the steps of: arranging the substrates in the substrateholder such that front surfaces or back surfaces of the substratesvertically adjacent to each other face each other; and setting a firstdistance between one of a first pair of substrates that are verticallyadjacent each other and have respective front surfaces facing each otherand the other of the first pair of substrates to ensure uniformity ofthe treatment, and setting a second distance between one of a secondpair of substrates that are vertically adjacent each other and haverespective back surfaces facing each other and the other of the secondpair of substrates to be smaller than the first distance.
 2. The heattreatment method according to claim 1, wherein the substrate holder iscomposed of two holder constituting bodies, and each of the holderconstituting bodies has a plurality of columns each including aplurality of substrate holding sections, the substrate holding sectionsof each of the holder constituting bodies being arranged at apredetermined vertical interval and adapted to hold circumferentialportions of the substrates, the columns being arranged on thecircumference of the same imaginary circle; one of the holderconstituting body holds the substrates under the condition that thefront surfaces of the substrates face upward, and the other the holderconstituting body holds the substrates under the condition that the backsurfaces of the substrates face upward, so that the substrate with thefront surface facing upward and the substrate with the back surfacefacing upward are alternately arranged in a vertical direction; and atleast one of the two holder constituting bodies moves up and down tochange the positions of the two holder constituting bodies relative toeach other so that the first distance is set to ensure the uniformity ofthe treatment and larger than the second distance.
 3. The heat treatmentmethod according to claim 2, further comprising the step of pivoting atleast one of the two holder constituting bodies in the circumferentialdirection to change the positions of the two holder constituting bodiesrelative to each other so that the columns of the two holderconstituting bodies surround the circumferential portions of thesubstrates under the condition that a distance between any two of thecolumns is smaller than the diameters of the substrates.
 4. A heattreatment apparatus comprising: a substrate holder for holding aplurality of substrates arranged at predetermined vertical intervals;and a heat treating furnace for receiving the substrate holder andallowing a predetermined heat treatment to be performed on thesubstrates therein, wherein the substrate holder has a plurality ofsubstrate holding sections for holding end portions of the substratesunder the condition that the substrate having a front surface facingupward and the substrate having a back surface facing upward arealternately arranged in a vertical direction; and the substrate holdingsections are arranged such that a first distance between one of a firstpair of substrates that are vertically adjacent each other and haverespective front surfaces facing each other and the other of the firstpair of substrates is set to ensure uniformity of the treatment andlarger than a second distance between one of a second pair of substratesthat are vertically adjacent each other and have respective backsurfaces facing each other and the other of the second pair ofsubstrates.
 5. The heat treatment apparatus according to claim 4,wherein the substrate holder is composed of two holder constitutingbodies, each of the holder constituting bodies having a plurality ofcolumns each including a plurality of substrate holding sections, thesubstrate holding sections of each of the holder constituting bodiesbeing arranged at a predetermined vertical interval and adapted to holdcircumferential portions of the substrates, the columns being arrangedon the circumference of the same imaginary circle; one of the holderconstituting body holds the substrates under the condition that thefront surfaces of the substrates face upward, the other of the holderconstituting body holds the substrates under the condition that the backsurfaces of the substrates face upward, and the two holder constitutingbodies are combined such that the substrate with the front surfacefacing upward and the substrate with the back surface facing upward arealternately arranged in the vertical direction; and at least one of thetwo holder constituting bodies is capable of moving up and down by avertical movement mechanism to change the positions of the two holderconstituting bodies relative to each other in order to ensure that thefirst distance is set to ensure the uniformity of the treatment andlarger than the second distance.
 6. The heat treatment apparatusaccording to claim 5, wherein a substrate holder rotating mechanism isprovided under a lid for closing a furnace throat of the heat treatingfurnace and has a rotating shaft; and the vertical movement mechanismhas an elevation shaft and an elevation drive section, the elevationshaft extending through the rotating shaft of the substrate holderrotating mechanism and being capable of moving up and down, theelevation drive section being adapted to cause the elevation shaft tomove up and down.
 7. The heat treatment apparatus according to claim 5,wherein a thermal insulation tube is provided on the lid for closing afurnace throat of the heat treating furnace, the vertical movementmechanism is composed of an elevation mechanism and a latch mechanism,the elevation mechanism being adapted to carry the holder constitutingbodies of the substrate holder into and out of the heat treatingfurnace, the latch mechanism being adapted to latch one of the holderconstituting bodies when the substrate holder is carried out of the heattreating furnace to restore the relationship between the position of theone of the holder constituting bodies relative to the position of theother of the holder constituting bodies.
 8. The heat treatment apparatusaccording to claim 5, further comprising a pivoting mechanism forpivoting at least one of the two holder constituting bodies in thecircumferential direction to change the positions of the two holderconstituting bodies relative to each other in order to ensure that thecolumns of the holder constituting bodies surround the circumferentialportions of the substrates under the condition that a distance betweenany two of the columns is smaller than the diameters of the substrates.9. The heat treatment apparatus according to claim 8, wherein asubstrate holder rotating mechanism is provided under the lid forclosing a furnace throat of the heat treating furnace and has a rotatingshaft, and the pivoting mechanism has an elevation shaft extendingthrough the rotating shaft and being capable of pivoting and moving upand down the holder constituting body.
 10. The heat treatment apparatusaccording to claim 8, wherein the pivoting mechanism is composed of alatch mechanism and a substrate holder rotating mechanism, the latchmechanism being adapted to latch one of the holder constituting bodieswhen the substrate holder is carried out of the heat treating furnace inorder to restore the relationship between the vertical position of theone of the holder constituting bodies relative to the vertical positionof the other of the holder constituting bodies, the substrate holderrotating mechanism being adapted to pivot the other of the holderconstituting bodies in the circumferential direction by a predeterminedangle with respect to the holder constituting body latched by the latchmechanism.
 11. A heat treatment method, in which a plurality ofsubstrates to be treated is held by a substrate holder at predeterminedvertical intervals, the substrate holder is carried into a heat treatingfurnace, and a predetermined heat treatment is performed on thesubstrates, comprising the steps of: forming a multi-plate unit thatuses a support ring to hold circumferential portions of two substratesunder the condition that back surfaces of the two substrates face eachother; and holding a plurality of the multi-plate units by means of thesubstrate holder at a vertical interval larger than a distance betweenthe front surface of one of the two substrates held by the multi-plateunit and the back surface of the other of the two substrates such that afirst distance between one of a first pair of substrates that arevertically adjacent each other and have respective front surfaces facingeach other and the other of the first pair of substrates is larger thana second distance between one of a second pair of substrates that arevertically adjacent each other and have respective back surfaces facingeach other and the other of the second pair of substrates.
 12. The heattreatment method according to claim 11, wherein each of the supportrings has a first support ring and a second support ring, each of thefirst support rings being adapted to hold the substrate under thecondition that the back surface of the substrate faces upward, each ofthe second support rings being adapted to hold the substrate under thecondition that the front surface of the substrate faces upward.
 13. Theheat treatment method according to claim 12, wherein each of the firstand second support rings has protrusions that protrude from thecircumference thereof and are arranged at a predetermined interval, theprotrusions of the second support ring of each of the support ringsbeing placed on the protrusions of the first support ring of the supportring, and having respective thicknesses that allow a distance betweenthe substrate held by the first support ring and the substrate held bythe second support ring to be maintained to a predetermined value.
 14. Aheat treatment method, in which a plurality of substrates is held by asubstrate holder at predetermined vertical intervals, the substrateholder is carried into a heat treating furnace, and a predetermined heattreatment is performed on the substrates, comprising the steps of:holding the substrates at predetermined vertical intervals by means ofthe substrate holder under the condition that back surfaces of thesubstrates face upward; forming a single-plate unit that uses a supportring to hold a circumferential portion of one of the substrates underthe condition that a front surface of the substrate faces upward;causing the substrate holder to hold a plurality of the single-plateunits by means of the support rings under the condition that the backsurface of the substrate held by each of the single-plate units and theback surface of the substrate that is held by the substrate holder andlocated directly under the substrate held by the single-plate unit faceeach other such that a first distance between one of a first pair ofsubstrates that are vertically adjacent each other and have respectivefront surfaces facing each other and the other of the first pair ofsubstrates is larger than a second distance between one of a second pairof substrates that are vertically adjacent each other and haverespective back surfaces facing each other and the other of the secondpair of substrates.
 15. The heat treatment method according to claim 13,wherein the substrate holder has a plurality of columns surrounding theend portions of the substrates; and each of the columns has claws andunit support sections, the claws holding the substrates, the unitsupport sections holding the single-plate units by means of theprotrusions of the support rings.
 16. A heat treatment apparatus forholding a plurality of substrates at predetermined vertical intervals bymeans of a substrate holder, carrying the substrate holder into a heattreating furnace, and performing a predetermined heat treatment on thesubstrates, wherein the substrate holder has a plurality of supportrings and a plurality of columns, the support rings holdingcircumferential portions of the substrates to constitute a plurality ofmulti-plate units under the condition that back surfaces of twosubstrates held by each of the multi-plate units face each other, eachof the columns having claws arranged in a vertical direction, the clawsholding the support rings that hold the substrates such that a distancebetween upper surfaces of the claws vertically adjacent to each other islarger than a distance between the front surface of one of the twosubstrates held by the multi-plate unit and the back surface of theother of the two substrates, and a first distance between one of a firstpair of substrates that are vertically adjacent each other and have therespective front surfaces facing each other and the other of the firstpair of substrates is larger than a second distance between one of asecond pair of substrates that are vertically adjacent each other andhave the respective back surfaces facing each other and the other of thesecond pair of substrates.
 17. The heat treatment apparatus according toclaim 16, wherein each of the support rings has a first support ring anda second support ring placed on the first support ring, each of thefirst support rings being adapted to hold the substrate under thecondition that the back surface of the substrate faces upward, each ofthe second support rings being adapted to hold the substrate under thecondition that the front surface of the substrate faces upward.
 18. Theheat treatment apparatus according to claim 17, wherein each of thefirst and second support rings has protrusions that protrude from thecircumference thereof and are arranged at a predetermined interval, andthe protrusions of the second support ring of each of the support ringsare placed on the protrusions of the first support ring of the supportring, and have respective thicknesses that allow a distance between thesubstrate placed on the first support ring of the support ring and thesubstrate placed on the second support ring to be maintained to apredetermined value.
 19. A heat treatment apparatus for holding aplurality of substrates at predetermined vertical intervals by means ofa substrate holder, carrying the substrate holder into a heat treatingfurnace, and performing a predetermined heat treatment on thesubstrates, wherein the substrate holder has a plurality of columns anda plurality of support rings, each of the support rings holding acircumferential portion of one of the substrates to constitute asingle-plate unit under the condition that a front surface of thesubstrate held by the single-plate unit faces upward; each of thecolumns has claws and unit support sections, the claws of each of thecolumns holding the substrates at the predetermined vertical intervalunder the condition that the back surfaces of the substrates faceupward, the unit support sections holding the single-plate units bymeans of the support rings under the condition that the back surface ofthe substrate held by the claws and the back surface of the substratethat is held by the single-plate unit and located directly above thesubstrate held by the claws face each other; and a first distancebetween one of a first pair of substrates that are vertically adjacenteach other and have the respective front surfaces facing each other andthe other of the first pair of substrates is larger than a seconddistance between one of a second pair of substrates that are verticallyadjacent each other and have the respective back surfaces facing eachother and the other of the second pair of substrates.
 20. The heattreatment apparatus according to claim 19, wherein the support ring ofeach of the single-plate units has protrusions that protrude from thecircumference thereof and are arranged at an appropriate interval, andthe unit support sections hold the protrusions.